Stroboscopic device

ABSTRACT

A stroboscopic device for checking the details of a cyclic work performed on a sheet or web in a machine, notably a print made in a rotary printing-machine. It comprises an optical fibre having one end disposed in close proximity of the flash lamp located at a certain distance from the web and the other end located in close proximity of said web so as to illuminate an area where a detail of the work being accomplished is to be checked, said area, due to its intermittent illumination by the light emitted by the flash lamp and transmitted through said optical fibre, appearing as stationary to the observer.

Elite twee tent 1 Corse Sept. 25, 1973 [54] STRQBOSCOPEQ DEVHCE I 1,904,124 4/1933 Cockrell 356/23 [75] Inventor: Louis Curse, Paris, France Primary ExaminerDavid Schonberg [73] Assxgnee: Chamboln Automation Sari, Paris, Assistant Examiner comad Clark France Attorney-Robert E. Burns et a1. [22] Filed: Sept. 7, 19711 Appl. No; 178,006

[ 5 7 ABSTRACT A stroboscopic device for checking the details of a cyclic work performed on a sheet or web in a machine, notably a print made in a rotary printing-machine. It comprises an optical fibre having one end disposed in close proximity of the flash lamp located at a certain distance from the web and the other end located in close proximity of said web so as to illuminate an area where a detail of the work being accomplished is to be checked, said area, due to its intermittent illumination by the light emitted by the flash lamp and transmitted through said optical fibre, appearing as stationary to the observer.

7 Claims, 1 Drawing Figure STROEOSCOIPIQ DEVICE BACKGROUND OF THE INVENTION The present invention relates in general to stroboscopic devices and has specific reference to a device of this character specially intended for checking the details of a cyclic work performed on a sheet or web.

Whenever work such as printing or the like is performed on a web travelling continuously through a machine, for instrance a rotary printing-machine, some means must be provided to enable the operator of the machine to check from time to time the quality of the printing thus produced. While such checking can easily be performed in the specific case of a web printed with spaced items and subsequently cut into separate sheets (so that sheets can be taken at random for inspection), this method is not applicable to a continuous web printed and subsequently wound on a take-up drum at the exit end of the machine.

Stroboscopic devices are already known which permit checking such continuous printed web by a visual method. As a rule, these devices comprise a generator producing a pulse during each cycle of operation and a flash lamp receiving said pulse, whereby the periodic lighting of said flash lamp, due to the stroboscopic effect, permits checking either by direct vision or through the medium of a suitable optical observation device, the quality of the work performed on the web.

In hitherto known stroboscopic devices the flash lamp and the optical observation device are mounted above the web on a movable support, and constitute therefor a relatively cumbersome and scarcely convenient assembly.

On the other hand at each cycle the flash lamp illuminates a very wide area of the web and in many cases, notably in printing processes, only an area of very reduced dimensions requires a very accurate examination SUMMARY OF THE INVENTION It is the essential object of the present invention to avoid the inconveniences of known stroboscopic devices by providing a particularly simple device characterized inter alia by great flexibility in operation.

To this end, the stroboscopic device according to this invention for checking the details of an object area or cyclic work performed on a sheet or web in a machine notably a print made in a rotary printing machine, comprises means for developing a pulse signal comprising a pulse generator adapted to deliver a pulse upon each cycle of operation of the machine, illuminating means comprising a light source such as a flash lamp disposed away from the sheet or web and connected to said generator in order to emit a flash each time a pulse is fed thereto, and means coacting with the illuminating means including an optical observation device mounted in the vicinity of the area to be checked and permitting the observation thereof, and an optical fibre having an input end disposed in close proximity of said flash lamp and an output end kept in close vicinity of said sheet or web for illuminating the area where a detail of the work performed must be checked and which, due to its intermittent illumination by the light emitted by said flash lamp and transmitted through said optical fibre, appears as a stationary detail to the observer.

BRIEF DESCRIPTION OF THE DRAWING A typical form of embodiment of the present invention will be now described by way of example with reference to the single FIGURE of the attached drawing illustrating diagrammatically a stroboscopic checking device associated with a rotary printing-machine performing cyclic printing operations on a web travelling continuously through the machine DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the rotary-printingmachine equipped with the device according to this invention comprises one or a plurality of printing units depending upon whether the printing is to be made in one or several colours, each printing unit comprising in turn printing cylinders of which one is shown diagrammatically at l in the drawing. This cylinder 1 is adapted to print cyclically on a paper web 2 travelling continuously through the rotary printing-machine between said printing cylinder 1 and an impression cylinder la. The print 3 formed on the paper web 2 is reproduced with a length corresponding to the printing format or size.

' The print checking device according to this invention comprises a pulse generator 4 adapted to deliver an electric pulse at each revolution of the printing cylinder 1, i.e. for each printed image 3. This generator 4 may be of any known and suitable type, whether electrical, magnetic, photoelectric electronic, etc In the exemplary form of embodiment illustrated in the drawing a photo-electric pulse generator is contemplated and comprisesa disk 5 operatively connected to the shaft of cylinder l and formed with hole an aperture or notch 6 moving along a circular path so as to block periodically a light beam emitted by a light source 7 towards a light sensitive device such as a photocell 8. Thus, during each revolution of the cylinder 1 the generator emits a pulse when the hole or notch 6 lies in the light beam between the light source 7 and photocell 8. This electric pulse is fed to an amplifier 9 having its output connected to illuminating means including a flash lamp 10 mounted in an opaque case 11. This case 11 is open on one side and means coacting with illuminating means is operative to close this side by a door 12 hinged mounted to the case 11. Secured to the hinged door 12 is the output end 13a of an optical fibre l3 having its other end or output end 13b disposed and kept in close proximity of the paper web 2, adjacent to specific area 3a of the printed image 3 of which it is desired to check the details. On the other hand, the

, mounted to movable supporting means comprising a support 15 adjustable across the web 2. Also secured to this support 15 is the output end 13b of said optical fibre 13. This end 13b is directed towards the web area lying around the line of sight of the observation device 14.

The above-described device operates as follows:

When it is desired to check the details of the printing in a predetermined area 3a of the printed image 3, the support 15 of the optical observation device 14 is moved across the web until this device lies above the path followed by the aforesaid area 3a. Then, the web 2 is illuminated directly and periodically by means of the flash lamp 10 by keeping the door 12 open. The lamp 9 emits a flash at each revolution of cylinder 1, the moment at which this flash occurs depending on the angular. timing of disk 5 in relation to the printing cylinder 1. Under these conditions it is possible, by variable delay means including means for manually modifying the timing of disk 5, to cause the flash lamp to be energized just when the area 30 to be checked is aligned with the line of sight of the optical observation device 14. Having thus preset the device the operator recloses the door 12 and then secures the case 11 magnetically or through any other suitable means to a suitable support. Thus, the light produced during the emission of each flash by the lamp 10 is transmitted through the optical fibre 13 to the output end 13b thereof so as to illuminate only the area 3a of the printed image 3 which it is desired to check. Due to the intermittent illumination of the area 30, which is synchronized with the working cycle of the machine, the illuminated area will thus appear as if it were stationary to the observer, due to the stroboscopic effect, so that the quality of the print in the checked area can be examined very carefully.

By shifting transversely the support 15 of the optical observation device 14 and modifying the angular setting or timing of disk 5, it is possible to check details in any desired area of the printed image.

The device according to this invention is applicable to the checking of any type of work, not only in the printing field, provided that it is performed cyclically on a sheet or web.

When it is desired to shift from one observed area 3a to another, it is also possible to more longitudinally the optical observation device 14 without altering the angular setting or timing of disk 5.

Although a single form of embodiment of the present invention has been described and illustrated herein, it will readily occur to those conversant with the art that various modifications may be brought thereto without departing from the basic principle of the invention, as set forth in the appended claims.

What I claim is:

l. A stroboscopic device for checking the details of an object area on a sheet or web in a machine, notably a print made in a rotary printing machine, which comprises a pulse generator operative to deliver a pulse upon each cycle of operation of the machine, a flash lamp disposed away from the sheet or web and connected to said generator for emitting a flash each time a pulse is fed thereto, an optical observation device mounted in the vicnity of the object area to be checked and permitting the observation thereof, an optical fibre having an input end disposed in close proximity to said flash lamp and an output end kept in close proximity to said sheet or web for illuminating the object area where a detail must be checked and which, due to its intermittent illumination by the light emitted by said flash lamp and transmitted through said optical fibre, appears as a stationary detail to the observer and means comprising an opaque case for having said flash lamp and a movable, hinged door closing one side of said opaque case, the input end of said optical fibre being secured to and through said movable door for illuminating the whole object area when said door is open and for illuminating a detail of said object area when said door is closed.

2. Device as set forth in claim 1, which comprises support means movable across said sheet or web for supporting said optical observation device and said out put end of said optical fibre, said output end being directed, in said support, towards the sheet or web area lying in axial alignment with the line of sight of the optical observation device.

3. A stroboscopic device for viewing object object areas periodically passing a viewing zone comprising: means for developing a pulse signal synchronous in time with the passing of each object area through a viewing zone; illuminating means responsive to each pulse signal for illuminating each object area in its entirety while same is in said viewing zone and comprising a light source, and an opaque housing having said light source mounted therein and having means therein defining an aperture; and means coacting with said illuminating means for selectively illuminating only a small portion of each object area while same is in said viewing zone and comprising a movable cover member for covering and uncovering said aperture, a light transmission member for transmitting light energy from one end thereof to the other end thereof, and mounting means mounting said one end of said light transmission member in said movable covermember for receiving light energy from said light source when said cover member covers said aperture and mounting said other end of said light transmission member in a position to illuminate a small portion of each object area.

4. A stroboscopic device according to claim 3; wherein said mounting means includes movable suporting means for movably supporting said other end of said light transmission member to effect illumination of selected small portions of each object area.

5. A stroboscopic device according to claim 3; wherein said light transmission member comprises at least one optical fiber.

6. A stroboscopic device according to claim 3; wherein said means for developing a pulse signal comprises variable delay means for delaying each of said pulse signals thereby variably delaying the illumination of each small portion of each object area passing through said viewing zone.

7. A stroboscopic device according to claim 6; wherein said means for developing a pulse signal comprises a light source, a light sensitive device responsive to light energy from said light source for developing a signal, a rotatable shaft rotably driven synchronous in time with the passing of each object area through said viewing zone, a timing disc having means therein defining an aperture and mounted on said shaft and positioned between said light source and said light sensitive device to periodically align said aperture therebetween to permit light energy to pass therethrough whereby said light sensitive device develops signal pulses during rotation of said timing disc corresponding in time to the passing of light energy through said aperture in each rotation of said timing disc; and wherein said variable delay means comprises means mounting said timing disc on said shaft for rotation therewith and therearound for selectively adjusting the angular position of said aperture relative to said shaft thereby delaying the occurrence of each signal pulse developed by said light sensitive device relative to the passing of each object area through said viewing zone. 

1. A stroboscopic device for checking the details of an object area on a sheet or web in a machine, notably a print made in a rotary printing machine, which comprises a pulse generator operative to deliver a pulse upon each cycle of operation of the machine, a flash lamp disposed away from the sheet or web and connected to said generator for emitting a flash each time a pulse is fed thereto, an optical observation device mounted in the vicnity of the object area to be checked and permitting the observation thereof, an optical fibre having an input end disposed in close proximity to said flash lamp and an output end kept in close proximity to said sheet or web for illuminating the object area where a detail must be checked and which, due to its intermittent illumination by the light emitted by said flash lamp and transmitted through said optical fibre, appears as a stationary detail to the observer and means comprising an opaque case for having said flash lamp and a movable, hinged door closing one side of said opaque case, the input end of said optical fibre being secured to and through said movable door for illuminating the whole object area when said door is open and for illuminating a detail of said object area when said door is closed.
 2. Device as set forth in claim 1, which comprises support means movable across said sheet or web for supporting said optical observation device and said output end of said optical fibre, said output end being directed, in said support, towards the sheet or web area lying in axial alignment with the line of sight of the optical observation device.
 3. A stroboscopic device for viewing object object areas periodically passing a viewing zone comprising: means for developing a pulse signal synchronous in time with the passing of each object area through a viewing zone; illuminating means responsive to each pulse signal for illuminating each object area in its entirety while same is in said viewing zone and comprising a light source, and an opaque housing having said light source mounted therein and having means therein defining an aperture; and means coacting with said illuminating means for selectively illuminating only a small portion of each object area while same is in said Viewing zone and comprising a movable cover member for covering and uncovering said aperture, a light transmission member for transmitting light energy from one end thereof to the other end thereof, and mounting means mounting said one end of said light transmission member in said movable cover member for receiving light energy from said light source when said cover member covers said aperture and mounting said other end of said light transmission member in a position to illuminate a small portion of each object area.
 4. A stroboscopic device according to claim 3; wherein said mounting means includes movable suporting means for movably supporting said other end of said light transmission member to effect illumination of selected small portions of each object area.
 5. A stroboscopic device according to claim 3; wherein said light transmission member comprises at least one optical fiber.
 6. A stroboscopic device according to claim 3; wherein said means for developing a pulse signal comprises variable delay means for delaying each of said pulse signals thereby variably delaying the illumination of each small portion of each object area passing through said viewing zone.
 7. A stroboscopic device according to claim 6; wherein said means for developing a pulse signal comprises a light source, a light sensitive device responsive to light energy from said light source for developing a signal, a rotatable shaft rotably driven synchronous in time with the passing of each object area through said viewing zone, a timing disc having means therein defining an aperture and mounted on said shaft and positioned between said light source and said light sensitive device to periodically align said aperture therebetween to permit light energy to pass therethrough whereby said light sensitive device develops signal pulses during rotation of said timing disc corresponding in time to the passing of light energy through said aperture in each rotation of said timing disc; and wherein said variable delay means comprises means mounting said timing disc on said shaft for rotation therewith and therearound for selectively adjusting the angular position of said aperture relative to said shaft thereby delaying the occurrence of each signal pulse developed by said light sensitive device relative to the passing of each object area through said viewing zone. 